Fluid pumps, motors and methods therefor



July 18, 1961 w. c. NILGES 2,992,619

FLUID PUMPS, MOTORS AND METHODS THEREFOR Filed Aug. 5, 1950 4 Sheets-Sheet 1 July 18, 1961 w. c. NlLGEs FLUID PUMPS, MoToRs AND METHODS THEREFDR 4 Sheets-Sheet 2 Filed Aug. 5, 1950 l l l l l l l l l l l l l l I 1 l l l l l l l l 1 l l 1 I l l l l l l l Fig; 9

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FLUID PUMPS, Mo'roRs AND METHODS THEREFOR 4 Sheets-Sheet 4 Filed Aug. 5, 1950 ig. l5

United States Patent 2,992,619 FLUID PUMPS, MOTRS AND METHODS THEREFOR William C. Nilges, Fairview Park, Ohio Filed Aug. 5, '19:50, Ser. No. 177,807 3 Claims. 4(Cl. ID3- 162) My invention relates to uid pumps, `hydraulic pumps, fluid motors, or compressors and the ter-m uid includes either hydraulic or pneumatic devices, and relates further to an improved method of actuating pistons employed in such devices.

In pumps or motors of the prior art with which I am familiar, a multiplicity of pistons are generally disposed in such relation to the piston actuating surface as to achieve relative rotation by the drive shaft of the piston actuating surface, such as, a swash plate or tilt plate in an axial design, or of a ring or track member in a radial design, and the cylinder block, and in such purnps or motors `a versed sine movement is commonly imparted to said pistons, the speed curve of which is represented .by a sine curve.

However, in most Huid pumps of the prior art with -.which I am familiar, such pumps, motors, etc. have .required a multiplicity of pistons to achieve substantial uniformity of flow and the variations in output and Ltorque have been compensated for in various ways. The more usual methods involve the addition of pistons Iand linoperative or dwell periods for certain of the pistons.

Such proposals have been generally unsuited for use in nnedium and high speed pumps as impact loading is experienced by the pistons at the ends of their respective .strokes and further, in certain of these structures, the 4inlet porting may be excessively restricted with uneven- .ness of ow.

According to my invention, means are provided to :control motion of pistons used in said pumps or motors :whereby the output of the pump, motor, etc. is uniform Vat `all times and constant, fewer pistons being necessary than in any prior art structure, due to the fact that, in my invention, the scalar sum of speeds of the pistons are .always maintained constant `by the said means.

It is an object of my invention therefor to provide a fluid device in Awhich piston acceleration is slowly developed from dead center or position to a maximum, ,which results in a smooth running fluid device.

Another object of my invention is to provide a iluid .fdevice such as a fluid pump, motor or the like whereby L,uniform output of fluid is achieved.

Another object of my invention is to provide a iluid device Where, aided by the relatively slow pickup of the piston velocity at dead centers with respect to the uid intake and discharge, a greater seal or overlap is achieved, `and hence leakage during the time that the cylinder passes from communication with the pressure outlet to Communication to the suction outlet is eliminated.

A further object of my invention is to provide a fluid i device of the type described wherein fewer pistons will be employed, said device lbeing simple in construction, cornposed of but few parts, economical in manufacture, and `highly eicient in use.

Another object of my invention is to provide irnprove- Y A still further object of my invention is to provide an b f. ICC

improved piston return for the devices of the character described.

Other objects of my invention and the invention itself ywill become more readily apparent by reference to the figures of drawing appended hereto and to the accompanying description.

In the drawings:

FIG. l is a transverse sectional view in perspective of a four cylinder axial type pump showing my invention inf conporated therein;

FIG. 2 is a perspective view of the valve plate FIG. l;

FIG. 3 is an elevational view of the rear surface the cover of FIG. l;

FIG. 4 is a view taken on the line 4-4 of FIG.

FIG. 5 is a front elevational view of the cover FIG. 3;

FIG. 6 is a perspective view of the cam of FIG.V

fFIG. 7 is a sectional View taken on the line 7--7 FIG. 1;

FIG. 8 is a sectional view taken on the line 8--8 FIG. 7;

FIG. 9 is an exploded View of the piston or cam follower ,o f FIG. 1;

FIG. 10 is a top plan view of the cam of FIG. 6 showing a cam follower lof one piston and its relation to the cam, diierent operative positions of the cam follower being shown in dotted lines;

FIG. 1l is a sectional view taken on the line 11 -11 of FIG. 10;

FIG. 12 is an end view of another embodiment of my invention, viz. a four cylinder rotary type pump showing my invention applied thereto; i

FIG. 13 is a transverse sectional View of the rotary type pump or motor of FIG. 12;

FIG. 14 is a view of the cam of FIGS. 12 and 13 and shows operative movement ot the piston therewith, as well as travel thereof and total stroke s as well as stroke x which is `the stroke at any angle of theta;

FIG. 15 is a graph of the piston stroke x of the form of my invention shown in FIGS. 1 and 12, using theta as an abscissa and 0 to pi as the range of drive shaft angle; equations thereunder representing said graph.

Referring now to the figures of `drawing in all of which like parts are designated by like reference chiaracters, and referring more particularly to the embodiment of my invention illustrated in FIGS. l to 1l inclusive, I show at 10 a casing or housing for a fluid pump or motor, the term fluid comprehending either hydraulic or pneumatic devices.

A cover or head 11 for said casing, secured to the said casing by tie bolts 12 or the like, is provided with an inlet port 13 and an outlet port 14 communicating by means of an inlet or suction side passageway `13, and an outlet or pressure side passageway 14 with cylinders 15', 16', 17 and 18 disposed with the cylinder block 19 rotatable Within the casing 10'. A longitudinally medially disposed motor shaft 20 mounted for rotation in said casing is splined to said block 19 by splines 20a and 20h which are located at opposite ends thereof. Spring means seated within a centrally disposed recess 121 within the cylinder block 19 is adapted to exert pressure against the shaft 20 to hold the same against seal means 122 to prevent the escape of uid at the motor end of the casing. The shaft is rotated by motor means (not shown) in a manner well known to the art. The cylinders are in the form shown in FIG. 1, equidistantly spaced from each other and from the shaft 20 and are disposed parallel to the shaft 20.

The substantially cylindrical outlet and inlet ports 13 and 14 are skewed at an angle to each other and the centrally disposed relatively narrow outer face21 of the l; of

head 11 is tapered from the mid-point or apex 22 thereof to each of the side faces 23 and 24 thereof. The passagevvays 13' and 14' terminate in kidney-shaped apertures 13" and 14" provided in a cylindrical end plate 26 integrally secured to the rear of the relatively wider inner face 25 of the head 11 and said apertures 13" and 14" communicate by valve means 27 with the cylinders 15, 16, 17 and 18. The head 11 is provided with a substantially vertically disposed bore 41 extending from a portion `42 of greater `diameter adjacent the upper surface of the head to a portion 43 of lesser diameter which intersects the centrally disposed open bore 44 which is an extension of the larger centrally disposed recess 45 which receives leakage uid from the kidney ports 13" and 14". In the portion 42 of the bore 41, a cornpression spring 46 is seated in a recess in the plug end cap 47, and said spring exerts pressure upon a ball 48 disposed therein to maintain a slight pressure on leakage fluid in the pump case. At the lower side of the head 11, an opening 49 communicates with the port portion 43 and the casing.

The valve means, as best shown in FIG. 2, comprises a circular valve plate 27 of slightly less diameter than the end plate 26 of the casing 11 and said valve plate is provided with a centrally disposed aperture 28 through which a circular end portion 29 of the cylinder block loosely projects, as best shown in FIG. 8. In equally spaced relation about the centrally disposed aperture 28 and concentric therewith a plurality of substantially elongated valve ports 3ft, prefer-ably four in number, are disposed. Said valve ports 30 are preferably equidistantly spaced about the outer periphery of said plate 27 and the diameter of said ports is substantially less than the land between the kidney ports 13" and 14 in the end plate 26 over which said plate 27 passes.

The disc 27 is superposed upon the inner valve face 25 of the head 11, as best illustrated in FIG. 3, and is provided with a peripherally disposed circular opening 31 through which a cylinder block pin 32 is projected to drive the valve plate and to align each of the ports 30 with a respective cylinder 15', 16', 17 and 18' and the inlet and outlet ports 13" and 14". The pin 32 is preferably of less diameter than the opening 31 as the end portion 29 is less diameter than the opening 28 to permit clearance to allow the plate to have a limiting tilting movement with respect to said cylinder block to compensate for any angular misalignment of the cylinder block with respect to the valve face and to keep the valve plate in intimate contact with the valve face of the cover 11 at all times eliminating uid leakage due to any cocking of the cylinder during rotation.

Each of the pistons 15, 16, 17 and 18 disposed within each of the cylinders 16', 17' and 18' comprises a cylindrical tube closed at one end 33 and open at their opposite ends 34, the inner face of said closed end 33 being bored to seat a cylindrical pin 35 which is projected within `a longitudinally bored `opening 36 within a spring guide 37, a portion of which is adapted to be telescoped within the piston, a piston return spring 38 of the compression type being adapted to encircle the guide, one end of said spring seating upon a shoulder 39 of each said guide. The opposite end of each said spring is piloted within a recess 40 within an annular end plug 40 disposed within a cover end of each cylinder 15', 16', 17' and 18', said plug being loosely mounted therein and sealed by a seal ring b thereof. The plug is seated upon the valve plate V217 by the spring force and by uid pressure acting upon the differential area a of cylinder bore and seat area, the seat area being of less diameter than said cylinder bore. Each plug `410 is aligned with each of the port openings 3i) in the valve plate 27. An opening 33' is preferably provided in the cylindrical walls of the pistons 33 to permit egress of uid therethrough to aid in the lubrication ofthe cylinder walls.

The closed end 33 of each piston is preferably rounded as best shown in FIGS. 1, 9 and 11 and is adapted to engage track surfaces 51 of a cam 50, formed as shown in FIG. 6. The cam 50 is preferably mounted as shown within the housing and telescoped over the drive shaft at the motor end thereof `and is fixed or non-rotatable therewith as described herein. The pistons 15, 16, 17 and 18 are adapted to rotate within the cylinders 15', 16', 17 and 18', and spin upon the track. The loads inducing a frictional force to cause this spinning action are caused primarily by the fluid pressure load on the pressure stroke of the piston land by the spring 38 acting through the spring guide 37 and pin 35 on the suction stroke of the piston. The spring 38, it will be noted, always exerts pressure upon the piston during the suction stroke of the piston and the cam must therefore, upon the pressure stroke, overcome fluid and spring pressures upon the piston.

The cam 50 is provided with a cylindrical mounting face centrally bored at 52 to receive the drive shaft 20 and is provided about its outer periphery with mounting apertures 53--53 adapted to receive screw means 54-54 which project into the same from the motor end of the casing 10. The track surfaces` 51 of the cam S0 are flat and have a downward radially extending substantially constant taper from the outer peripheral surfaces thereof to their inner peripheral surfaces, the cam surface in a circumferential direction rising slowly from the lowermost track surfaces t1 to a maximum rate of rise at track surfaces t2 intermediate the surfaces t1 and the surface t3, which is the surface of greatest height oppositely disposed to the surfaces Il.

The rate of rise of the piston producing the profile herein described for the cam is equal to a constant which is a function of the total stroke s and the number of pistons times the sine squared of a second constant which is a function of a number of pistons and the range of angular movement thereof times theta (which is the angle indicated at BOC, FIG. l0, the angle being drawn normal to both center line of the piston and the center line of the drive shaft and la line drawn from the intersecting line with the drive shaft) at t1 up to the point of inflection t2 at which point the rate of rise is constant followed by the same but inversed sine squared rate of rise curve t3.

The cam imparts to the pistons a piston velocity which varies directly. as the sine squared of a constant times the drive shaft angle, which is determined as theta (0).

In a four cylinder pump or motor of the type described, K2=1 and since the pistons are separated by 90 the reference piston will be driven at a velocity proportional to the sine squared of theta and a piston spaced therefrom, as indicated by ordinary trignometric considerations, will be driven at a velocity proportional to the co-sine `squared of theta; the net sum of the velocity of said pis- Jons being a constant and the fluid ow thus bei-ng uniorm.

'Iiheleft lhalf or pressure side of the cam track as viewed in FIG. 11, which is preferably identical with the right half or suction side of the cam track as shown, is developed `according to the shape of the cam follower to give a resulting mot-ion of the piston Vaccording to the integral and integrated equations and graph of FIG. l5 Where x is the travel of the piston measured from its extreme outward position and theta is the angle measured from bottom dead center `or fully extended position b and its position at any point from such bottom dead center-position B of the piston up to toprdead center or retracted position A, the angle being BOC, O being the center of rotation of the drive shaft. ,The integrated or aecomo J lowermost equation of FIG. vdescribes -a sine squared velocity or so-called cycloidal curve for the piston motion of the pump illustrated herein. rIlhe development of the cam track, it will be noted, is substantially such that the track comprises a curve equi-distant from the sine squared veloci-ty curve of the integrated equation.

The cam generated according to the formula set forth in FIG. 15 and described herein will therefore actuate the pistons in such manner that the scalar sum of the piston velocities on either side of dead center indicated at A-B will be a constant at any drive shaft angle. Although a horizontal fixed cam is shown in the form of my invention illustrated in FIGS. 1 to 11 inclusive, it will be apparent that the principle of my invention could be applied where the cylinder block is stationary and the cam rotates, as well as in `structures where the pistons and bores lie in a plane at right angles to the drive shaft, as in FIGS. 12, 13 and 14, or at some lesser angle.

In operation, in the form of FIG. l, iluid is drawn into lthe pump through the inlet port 13 upon the suction or forward stroke of the piston and discharged from the pump through the -discharge port 14 and in the rotation of the cylinder block successive cylinders are brought into communication with the suction and pressure passageways 14 and 13'.

Since ythe velocity of the pistons varies as the sine squared relationship, it will be obvious that piston velocity and rate of change of said piston velocity or acceleration at dead center positions A--B wiil be 0, and it will be apparent that piston velocity will change very slowly as compared with prior art structures in the so-called valve cross-over points A and B. Therefor a greater land between ports 13 and 14 may be provided, thus ensuring a greater fluid seal at such cross-over between intake and discharge ports. It `will be further noted that piston acceleration is greatest or at its maximum at an intermediate point between such dead center positions.

Referring now to the second embodiment of my invention -illustrated in FIGS. 12, 13, and 14, my invention is applied to a radial type fluid pump or motor having a symmetrical constant flow cam 203 encircling said pistons. The said cam 203 is developed as described above in connection with the cam of FIG. 1, according to the formula of FIG. 15. In this form of my invention, the drive shaft 220 is supported in the housing 208 by a bearing 209 located by means of a snap .ring 217 and secured to the cylinder `block 205 by screw or other securing means '210. The bearing 209 is retained by a seal plate 221 secured to -the housing 208 by screws 207. The cylinder block 205 and drive shaft 220 are further supported by the pintle journal 214 upon which the cylinder block is closely fitted but which block is still free to turn. The journal 214 has two fluid ports 215 and 216 terminating in port slots or passages 218 and 219 respectively centered on the piston axis and extending so that t-he apertures 21S and 219' respectively in the inner face of the cylinder block 205 are sealed by the land l between the slots whenever a pair o-f pistons 2310 lie on the line A-B as shown in FIG. 12. The pintle journal 2114 is secured to the rear of the housing 212 by means of screws 213. Housing sections 208 and 212 are secured together by screws 211 with the cam 203 interpositioned therebetween.

rlhe cylinder block 205 in the form of my invention illustrated in FIGS. 12, 13 and 14, is provided with a plurality of cylinder bores, preferably four in number, within which pis-tons 230 having roller cam followers 206, journalled for rotation therewith, bear against the raceway of cam 203. In FIG. 14, I show the displacement motion x measured along the pis-ton axis, which in this embodiment is inward in a radial direction. The quantities "s and theta are as defined hereinbefore in connection with the form of my invention illustrated in FIGS. l() and 1l. Rotation of the drive yshaft 220 causes reciprocation of the pistons, drawing in fluid through one'rport 2115 and discharging it -through the oppos-ite port 216 in a manner similar to the intake and dischange of fluid in that form of my invention shown in FIG. 1.

Piston return on the suction stroke is preferably achieved in this form of my invention illustrated in FIGS. 12, 13 and 14 by centrifugal force acting upon the piston. The pump of these figures is reversible, as ,will be readily understood, by changing the direction of rotation and consequent change of outlet and inlet connections.

Whenever I have referred in my speciiication to either cycloidal or sine squared velocity curve it will be understood that I am referring to Ithe type of displacement curve shown in lthe graph of FIG. 15 which depicts the piston displacement versus the angle of relative rotation between the piston actuating means -and/ or cam member and the piston or pistons for which the graph is applied.

`-Although I have described my invention in connection with preferred embodiments thereof, it will be obvious that numerous and extensive departures may be made therefrom, `such as employing a different number of pistons, etc., various positions thereof, various designs Ithereof, without, however, departing from the spirit of my invention or the scope of the appended claims.

What I claim is:

1. In a fluid device of the character described, a housing therefor, a cylinder block disposed within said housing, a plurality of cylinders disposed within said cylinder block, a plurality of pistons reciprocally mounted within said housing, motor actuated drive shaft means, a cam mounted at one end of the housing in fixed relation thereto, said drive shaft rotatable with said cylinder block, fluid inlet and outlet ports disposed at one end of said housing, valve means disposed between said inlet and outlet ports and said cylinders, said valve means being loosely driven by the said cylinder block, ports in said valve means communicating with said inlet and outlet ports and with said cylinders, the width of said valve ports being of less width than the land between said inlet and outlet ports, said valve means being so disposed with respect to said cylinder block as to have a limited tilting movement with respect t-o said cylinder block, said cam imparting to said pistons an acceleration which is zero at dead center position of said pistons.

2. In a uid device of the character described, a housing therefor, a drive shaft, a plurality of cylinders, a plurality of pistons slidably mounted within said cylinders, said pistons being hollow and having closed ends projecting from said cylinders, coil springs disposed in said cylinders, tapered spring guide members, a recess within said inner wall of the closed end of the pistons and a recess disposed within said tapered spring guide member,`

pin means seated at either end within each said recess,

annular closure members disposed at one end of said cylinders, said springs each being seated upon said spring;

guide and said closure member.

3. In a fluid device of the character described, a heus-- ing therefor, a drive shaft, a plurality of cylinders, a: plurality of pistons slidably mounted within said cyl-- inders, said pistons being hollow and having closed ends: projecting from said cylinders, coil springs disposed ini said cylinders, tapered spring guide members, a recesswithin said inner wall of the closed end of each said piston and a recess disposed within each said tapered spring guide member, pin means seated at either end.A within each said recess, an annular closure member disposed at one end of each said cylinder, said springs being seated upon said spring guide and said closure member, said pin means, guide means and spring means being reciprocably mounted within each said piston, and the piston spinning about its longitudinal axis and the longitudinal axis of said pin, lguide and spring means.,

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS Hardy May 31, 1910 Eizeman Feb. 17, 1914 5 Williams Apr. 16, 1918 Coursen Jan, 8, 1929 .Malm Oct. 11, 1932 Hawley Aug. 15, 1933 8 De Stoutz Nov. 17, 1936 Dell Oct. 15, 1940 Wright Mar. 29, 1949 Hoer Feb. 7, 1950 Heurichsen Aug. 25, 1953 FOREIGN PATENTS Great Britain Sept. 12, 1910 

